Nostr is a protocol, not a platform and as such needs to remain open and permission-less otherwise it is completely useless. This is the same way you can transmit controversial (and even illegal) messages over HTTPS and pay for the same using Bitcoin.
Any filtering and/or censorship has to be done at the relay/application level, allowing relay operators to decide which events they wish to store and relay, as well as users to choose what kind of content they get to see.
I am by no means a hardcore Libertarian or any of the -ist words that get thrown around so carelessly these days, but I do understand why we need an open and permission-less social media protocol.
The true test of such a protocol is if people you completely disagree with can use it too.